Move implementation of coeff() &c to Matrix/Array evaluator.
Move implementation of coeff() &c to Matrix/Array evaluator.

madlib/eigen_backup,madlib/eigen_backup,madlib/eigen_backup,mjbshaw/Eigen,madlib/eigen_backup,mjbshaw/Eigen,rotorliu/eigen,mjbshaw/Eigen,mjbshaw/Eigen,rotorliu/eigen,rotorliu/eigen,rotorliu/eigen